Sand conditioning equipment



0C1; 18, 1960 w, DIETERT ETAL 2,957,130

SAND CONDITIONING EQUIPMENT I FIG.5

INVENTORS HARRY w. DIETERT BY RANDOLPH L. DI ETERT 6 ATTORNEYS States Patent SAND CONDITIONING EQUIPMENT W. Dietert and Randolph L. Dietert, Detroit, Mich, assignors to Harry W. Dietert Company, Detroit, M1ch., a corporation of Michigan 2 Claims. Cl. 324-61) The present invention relates to sand conditioning equipment, and more particularly to apparatus for mixing sand and water including means exposed to the mixture for determining its moisture content.

The present application is a division of our prior copending application Serial No. 613,075, filed October 1, 1956, now Patent No. 2,863,191. 1

It is an object of the present invention to provide a moisture probe having a surface exposed to moist comminuted material including an insulated electrical conductor, and means for establishing the electrical capacitance between the conductor and ground.

More particularly, itis an object of the present invention to provide a moisture probe designed particularly for use in a sand mixing mill to have moist samples of sand compressed thereagainst to afford a moisture reading and thereafter removed, characterized in the substantially complete absence of stickiness which permits clean removal of a compressed sand specimen.

, It is a further object of the present invention to provide amoisture probe comprising a tube preferably of stainless steel having an end surface exposed within a receptacle, a di-electric bushing within said tube having an. end surface forming a smooth continuation of the end surface of the tube and also exposed to moist material in the container, and an electrical conductor extending through said tube and having a portion, preferably radially enlarged, the end surface of which is coplanar with the end surfaces of said tube and said bushing, said container being formed preferably of stainless steel 20 facilitate removal of compressed moist specimens there- -"-More specifically, it isan object of the present invention to provide a moisture probe as described in the preceding paragraphwhich comprises resilient means acting between the tube and electrical conductor and effective to maintaina tight assembly of said tube, bushing and conductor.

It is a further object of the present invention to provide a moisture .probe as described. in the foregoing in conjunction with electrical heating means to heat the moisture probe and particularly, the portion thereof exposed within the container to avoid continuation of moisture thereon.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing, illustrating preferred embodiments of the invention, wherein:

Figure 1 is a diagrammatic plan view of a sand container constructed in accordance with the present invention.

Figure 2 is a transverse sectional view of the structure shown in Figure 1.

Figure 3 is a diagrammatic plan view of a sand container forming a second embodiment of the present invention.

Figure 4 is a sectional view on the line 44, Figure 3.

2,957,130 Patented Oct. 18, 1960 FigureS is an axial section through the moisture determining probe employed in the present invention.

In the embodiment of the invention illustrated in Figure's 1 and 2, a quantity of moist sand indicated at S is in a container 10 which may be a conventional sand mill and which is mixed with water added thereto by the rotation of a pair of relatively heavy rollers 12 having scraping blades 14 and 16 rotatable therewith. Located in the bottom wall of the mill is a moisture probe 18 the details of which may be as described subsequently in conjunction with Figure 5. In operation, the moisture content of the sand is continuously determined by the moisture probe, the passage of each roller 12 over the moisture probe compressing a moist specimen and giving a relatively high or maximum reading of moisture content. Thereafter, the blade 14 passes over the moisture probe 18' and removes the moist sample therefrom. While moist sand may fall back against the moisture probe, it will not afford a high reading until passage of the next succeeding roller 12 thereover.

Preferably, the moisture probe is associated in a control system which continues to add water to the sand until a control system including the moisture probe indicates that the percentage of moisture is adequate.

Referring now to Figures 3 and 4 there is illustrated a second sand mill 20 having a rotary carrier 22 connected to a drive shaft 23 rotatable about a vertical axis and having rollers 24 adjacent its periphery. Depending from the carrier 22 are vanes 26 the lower edges of which are connected to a'plate 28. At the outer edges of the carrier 22 and in the horizontal plane of the rollers 24 are provided scrapers 30. The mixer also includes plows 32. Water is admitted to the container through a pipe 33 and the admission of Water is controlled by means responsive to the moisture content and also preferably to the temperature of the sand in the container 20. A thermocouple for determining temperature of the sand is indicated at 34 and a moisture probe is indicated at 36.

It will be appreciated that as the shaft'23 rotates, the rollers 24 compress specimens of moist sand against the exposed surface of the moisture probe 36 to effect a maximum reading. Thereafter, the moist specimen is removed by the next succeeding scraper 30 which follows each of the rollers 24. Accordingly, a series of independent readings of moisture content are taken each of which includes the step of compressing a new specimen of moist sand against the operating surface of the moisture probe at a constant pressure and thereafter removing the. compressed specimen.

In either case the operation depends for its accuracy on the control'of the addition of water upon the accuracy of readings of the moisture content.

The moisture probe illustrated in Figure 5 is adapted to provide-accurate readings of the moisture content in association with the structure shown in Figures 1-4.

The moisture probe comprises a tube 40 preferably formed of stainless steel and fixed in an opening 42 in a plate 44 adapted to be exposed at the inner surface of a wall of the container '10 or 20. Located within the tube 40 is a metal ring 46 fixed in position by pins 48. An insulating bushing 50 is provided having an opening 52 through which extends a stainless steel probe element 54 the inner end of which is conically formed as illustrated to engage in a conical seat 56 provided in the bushing. The inner surfaces of the tube 40, the bushing 50, and the probe 54 are all smooth continuations of the exposed surface of the plate 44. If the probe is located in the bottom wall of the mill the exposed surfaces are planar. If the probe is located in a side wall of the mill, the exposed surfaces are preferably cylindrically formed.

At the underside of the ring 46 is a second insulating member 58 having a reduced portion 60 carrying a washer 62 preferably formed of metal such for example as brass.

Slidabl'y supported in the tube 40is a third insulating member 64 having a reduced portion 66 carrying a Washer 68 formed of metal such for example as brass. Extending between the washers 62 and 68 is a compression spring 79. Located within the spring 70 and surround ing the intermediate portion of the probe element 54 is an insulating sleeve 72.

The outer end of the probe element 54 is threaded s indicated at 74 and carries a nut 76 bearing against Washer 78 which in turn bears against the outer end of the insulating member 64. Accordingly, the spring 79 urges the probe element 54 outwardly and maintains its head in firm contact in the conically formed seat provided in the bushing 59. The spring is also elfective to maintain the bushing 50 firmly against the annular seat afforded by the member 46. By adjusting the nut 76, the effectiveness of the spring 70 may be adjusted to insure a positive seal between the bushing 50, and probe element 54 at all times despite cold flow of the material of the bushing. The insulating members or bushings 50, 58 and 64 are formed of a suitable inert plastic material such as Teflon.

It has been found that unacceptably large errors in determination of moisture content may result if the moisan elongated metal tube having a substantially fiat first end and an annular shoulder therein spaced inwardly from said first end, an annular bushing of plastic material having one end seated on said shoulder having its other end substantially flush with the said first end of said tube, said bushing fitting closely within the first end portion of said tube, said bushing having a central opening extending therethrough in alignment with the axis of said tube, said opening at its other end being of outwardly flaring conical shape, an elongated central electrode having a conical head seated in the conical portion of the opening through said bushing, the end surface of said head being flush with the first end of said tube and the said other end of said bushing, and a shank extending longitudinally of said tube, an annular abutment on said shank adjacent the second end of said tube, a first insulating spring seat located against the side of said shoulder remote from said first end of said tube, a' second insulating spring seat located against the annular abutment of said shank, an elongated compression spring extending between said spring seats and urging said center electrode toward the said second end of said tube to apply forces through its conical head axially and radially ture probe is at a temperature of less than that of the sand. In such case the moisture probe indicates a substantially greater moisture content for the sand than is actually present. In accordance with the present invention means are provided for insuring that the moisture probe is maintained at a temperature above that of the thermal insulation may be provided, as indicated at 86 to surround the tube 40.

The probe element 54 is connected to a conductor 88 of a coaxial cable indicated diagrammatically at 90, and thus, the electrical capacitance between the probe 56 and ground may be determined by appropriate connection of the coaxial cable to measuring instruments. The actual electrical capacitance measured is the electrical capacitance surrounding the head of the probe element 54 and this is found to be a direct function of the moisture content of the moist material in the specimen compressed against the surface of the probe. The drawing and the foregoing specification constitute description of the improved sand conditioning equipment in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What we claim as our invention is:

1. Probe structure for the measurement of the moisture content of moist granular material, said probe comprising of said insulating bushing while providing for yielding movement thereof on expansion of said bushing.

2. Apparatus for mixing a granular material and; a liquid and for measuring the moisture content of the granular material, comprising a receptacle having an opening in a wall thereof; an electrical probe positioned in said opening and having a moisture sensitive surface within said receptacle forming substantially a smooth continuous surface with the inner surface of said wall,

; means within said receptacle for mixing the granular material and liquid and operable to bring different portions of the moist granular material into contact with said moisture sensitive surface, said probe comprising a metal tube, a center electrode in said metal tube, and an insulating bushing interposed between said tube and center electrode, said tube extending outwardly of said receptacle, and a heater surrounding the exterior portion of said tube in heat transfer relation thereto to maintain the moisture sensitive surface of said probe at a temperature which is not less than the temperature of the moist granular material in said receptacle.

References Cited in the file of this patent UNITED STATES PATENTS 2,650,343 Thompson Aug. 25, 1953 2,702,948 Seney Mar. 1, 1955 2,755,438 Cudmore "1--..-- July 17,, 1956 2,802,178 Shafer et al. Aug. 6, 1957 2,824,282 Posey Feb. 18, 1958 2,852,740 Posey et a1. Sept. 16, -8

FOREIGN- PATENTS 116,478 Great Britain Feb. 4; 1943 We ..n....'.". 

